Crane hooks are generally required to be tied back for loading and transportation of the crane. The purpose of the tie back is to prevent damage to the crane boom and other crane carrier components potentially resulting from uncontrolled swinging of the crane hook load, or load block.
In a relatively common situation where the crane operator, due to some temporary inattentiveness or incapacitation, does not remove the tie back, typically a standard wire rope or a sling constructed of synthetic material, begins to advance the boom upward, that tie back will break once its ultimate tensile strength is exceeded, releasing the load block with destructive force.
It would therefore be advantageous to provide a physical indication, such as an audible or visible indication, to forewarn the crane carrier operator, and any bystanders, of a potentially destructive situation involving such a progressively increasing overload condition.